On Mon, 16 Apr 2007 08:01:07 +0200
Vincent Snijders <[EMAIL PROTECTED]> wrote:
> Mattias Gaertner schreef:
> > On Sun, 15 Apr 2007 23:01:28 +0200
> > Vincent Snijders <[EMAIL PROTECTED]> wrote:
> >
> >> Questions:
> >> * Is this code actually to be executed? Was it designed so that the
> >> IDE could execute this code at design time? I think the answer is
> >> yes.
> >
> > Short answer: yes
> > Long answer: It is the really dirty hack in the IDE.
> > It was done, because assigning a 'real' TMethod to an event has the
> > advantage that all OI, RTTI and all streaming code work without
> > hacks or additions.
>
> As expected.
>
> >
> >
> >> * I tested on windows XP 64. Does anybody know if the 64 bits
> >> version of windows works differently in this respect than the 32
> >> bits version? For example does it proctect the memory on the heap
> >> from execution?
> >
>
> Does anybody else *know* this? I am just guessing about the actual
> cause of the crash.
>
> I did an additional test. I replaced
> Result.Code:=NewCode;
> by
> Result.Code:=CodeTemplate;
> in TJITComponentList.CreateNewMethod. This fixed the crashes (but
> probably breaks something else).
>
> > If yes, then it is finally time to use the Delphi half Assigned
> > trick and to check and extend the whole OI, RTTI and Streaming code
> > to support this.
>
> How hard is this?
I'm not sure. Probably a good day work. The main problem could be FPC.
> Can you explain the half Assigned trick? Or is it
> faster for you to implement it. ;-)
The trick itself is easy:
TMethod contains two pointers: code (the address) and data (the
TObject). Normally you assign both and everything works normally. But
if you set only one of them nil, then the test "AMethod<>nil"
still is true, but "Assigned(AMethod)" gives false.
If all components always use "if Assigned(AMethod) then AMethod(...)",
then this trick prevents calling the method at designtime, while still
holding a pointer. The pointer can be used by the IDE to know, which
method name to stream.
I don't remember which of the pointers are set to nil by Delphi.
A quick test revealed: FPC's Assigned does not support this.
What needs to be changed:
FPC's Assigned, TReader, TWriter, TMethodPropertyEditor, jitforms and
all other places where AMethod.Code and AMethod.Data is used.
Of course this trick works only for methods, not procedures.
There are two alternatives:
1. set all events to nil and extend TReader and friends to use some
highly sophisticated method lookup.
2. Do it like msegui and add a
not (csdesigning in componentstate)
to every method check in every component. (not Delphi compatible)
Mattias
_________________________________________________________________
To unsubscribe: mail [EMAIL PROTECTED] with
"unsubscribe" as the Subject
archives at http://www.lazarus.freepascal.org/mailarchives
